1. Field
This invention relates to equipment adapted for use in performing physical exercises. More particularly, the invention is directed to equipment adapted for performing walking or running-type exercises.
2. State of the Art
Exercise equipment, of the type commonly designated as treadmills, conventionally includes a frame and a pair of end drums mounted thereon to be rotatable. An endless belt is trained over the drums to form a platform on which the user stands. Typically, one of the drums is drivingly rotated, thereby causing the endless belt to travel over the two drums. As the belt travels, it forms a moving platform on which the user may perform running or walking-type exercises.
As a user continues to use the treadmill over time, it becomes desirable to vary the speed of travel of the belt so as to either increase or decrease the degree of difficulty of the exercises being performed. In previously disclosed treadmill structures, a variation in the belt's speed has been obtained by the use of a variable speed electric drive motor connected to one of the drums. A typical speed adjustment arrangement of this type is disclosed in U.S. Pat. No. 3,606,320 (Erwin).
U.S. Pat. No. 4,635,928 (Ogden, et al.) discloses a motorized treadmill wherein an electric motor having a drive shaft is keyed to a variable speed pulley. The variable speed pulley in turn is aligned with a fixed speed pulley keyed to the drive drum roller of the treadmill. The two pulleys are mechanically intercooperated by a "V"-type pulley belt. The motor is pivotedly mounted to the treadmill frame whereby an angular rotation of the motor about its pivot axis effects a biasing action of the belt on the variable speed pulley which in turn causes a variation in the ratios of the two pulleys and a corresponding variation in the speed of the drive drum roller being rotated by the pulleys.
Another treadmill which utilizes a variable speed pulley unit to provide means of adjusting the speed of the belt is shown in U.S. Pat. No. 4,502,679 (DeLorenzo).
U.S. Pat. No. 4,792,134 (Chen) discloses a treadmill having a variable speed adjustment composed of two pairs of conical disks mounted coaxially on a transmission shaft disposed between the output shaft of the drive motor and the input shaft of the driven drum roller. Each disk pair includes a fixedly mounted disk and a slidable disk mounted adjacently to the slidable disk of the second pair of disks. The slidable disks are adapted to move mutually upon a lateral displacement of the transmission shaft. A transmission belt is interposed between the disks of each pair of disks, the disks forming a pulley over which the belt travels. As the disks slide along the transmission shaft, the effective ratios of the two disk-formed pulleys are varied, thereby effecting the speed of the input shaft of the driven drum roller.